Purification of vat dyestuffs of the anthraquinoneazine series



- Patented Feb. 28, .1933

entrant critics HEINRICH NERESHEIMER AND WILHELM"SCHNEIDER, or nunwrs-snnrnn-ou-rnnnninn, GERMANY, Assienons TO animus womrs, 13104013 new YORK,

11.15., A CORPORATION or DELAWARE PURIFICATION or var nYEsTUrrs or a e, nurnnaenrnounezinn snares No Drawing. Application filed March 1831, Serial 520,483, and in Germany March 10, 1930.

The present invention relates to the manu facture of vat dyestuffs of the N-dihydro- 122.21-anthraquinoneazin-e series which are fast to chlorine.

According to the process described in the U. S. Patent No. 785,l22 a vat dyestuif which dyes cotton pure green blue shades and generally of excellent fastness isobtained by the action of formaldehyde on N-dihydro- 1.2.2.1 anthraquinoneazine (Indanthrene blue RS, Color Index 192d, No. 1106) in acid solution. the objection that it has only a comparatively slight fastness to chlorine.

We have now found that dyestuffs producing dyeings which are considerably more fast to chlorine than those obtained with the dyestuff hereinbefore referred to are obtained by removing components not fast to chlorine from the condensation products obtainable from impure N dihydro 1.2.2.1-anthraqumoneazine and formaldehyde or agents supplying formaldehyde such as paraformaldehyde, methylal and glycolic acid, by

means of sulphuric acid of at least 70 per cent strength. By the term impure i d1hydro-1.2.2.1-anthraquinoneazine We 1ntend to define dyestuffs of the purity of the commercial lndanthrene blue RS (Color IndeX 1924, No. 1106). The removal of the comp onents not fast to chlorine may either be effected by fractionally precipitating the said condensation products from their solution in 4 concentrated sulphuric acid by dilution only to such an extent that the concentration of the sulphuric acid is not reduced to below 70 per cent strength, whereby the said com- .ponents not fast to chlorine remain dissolved in the sulphuric acid, or by extracting from the said condensation products, components not fast to chlorine by means of dilute sulphuric acid of at least 70 per cent strength. Dyestuffs giving more or less greenish blue dyeings are obtained by the process according tothe present invention depending on the amount of formaldehyde employed and on the reaction conditions. The purification may be effected for example by addmg Water either as such or in the form of dilute sulphuric acid in such an amount to a solution 7 To this d estufl there is however the dyestuffobtained by the treatment of;

impure commercial N-dihydro-L22.1-anthraquinoneazin-e in concentrated sulphuric acid with formaldehyde that the dyestuff fast to chlorine separates out. I I

lit is surprising that dyestuffs substantially faster to chlorine than the intitial material can be obtnined'in the said simple manner,

since on the one hand the condensation products oi ll-QllllYCllO-l.QQ'l ZIH'GhTQQUlHOHQ- azme and formaldehyde are considerably more soluble in fairly dilute sulphuric acid than N -dihydro-122.1anthraquinoneaZine itself and on the other hand it is known that the impurities not fast to chlorine present in commercial N dihydro-l .221 anthraq'uin- 4 are likewise comparatively soluble n fairly dilute. sulphuric acid as results from the solubilitics or" both products in fairly dilutesulphuric acid would be very small and a s-eparationby the said means would not be possible or degree,

.LllQ shades produced with the dyestuffs purified the manner hereinbefore described may be varied by' sub ecting the said dyeto a further treatment with alkalies or sing or halogenating agents.

The following examples will further illustrate how the said invention may be carried out in practice, but the invention is not re stricted to these examples. The parts are byweight.

Emma/gale 1 c l r C. to solution of 10 parts of commercial lndanthreneblue 51S ,(see Color Index,

tne U. 5%. Patent No. l,5ll,156. It was there- .1036 to be expected that the difference between possible only to an insufi'icient art of panaformaldehyde is added at which dyes cotton from a blue vat more greenish blue shades having a substantially better fastness to chlorine than the initial material. The impurities in the dyestuff which are not fast to chlorine may be precipitated from the mother liquor in the form of a greenish blue fiocculent pouring into water.

Encample 2 Indanthrene blue RS, commercial brand, is condensed with paraformaldehyde in the manner described in the foregoing example. The condensation product is recovered by pouring the reaction mixture into water, filtering oh the precipitate, washing and drying it. 10 parts of the 'dyestufi' thus obtained are finely ground and introducedat 15 G. into 100 parts of sulphuric acid of 85 per cent strength. The mixture is stirred at the said temperature until no more of the product passes into solution, the undissolved dyestuff then being filtered ofl' andworked up as usual. It dyes cotton from a blue vat shades very similar to those obtained with the dyestuff produced according to Examplel.

l Vhat we claim is 1. In the manufacture of vat dyestuffs of the N-dihydro-1.22.l-anthraquinoneazine series the step which comprises removing components not fast to chlorine from a condensation product of impure N-dihydro- 1.2.2.1-anthraquinoneazine and formaldehyde by means of sulphuric acid of at least per cent strength.

2. In the manufacture of vat dyestuffs of the N -dihydro-1.2.2.l-anthraquinoneazine series the step, which comprises dissolving a condensation product of impure N -dihydrol2.2.l-anthraquinoneazine and formaldehyde in concentrated sulphuric acid, diluting the solution by adding water in such amounts to reduce the concentration of sulphuric acid not below 70 per cent strength, and recovering the undissolved part of the said condensation product.

3. In the manufacture of vat dyestuffs of the N -dihydro-1.22.1-anthraquinoneazine series the step which comprises digesting a condensation product of impure N-dihydrol2.2.1-anthraquinoneazine and formaldehyde with sulphuric acid of at least 70 per 1 cent strength, and recovering the undissolved part of the'said condensation product.

In testimony whereof we have hereunto set our hands.

HEINRICH NERESHEIMER. WILHELM SCHNEIDER.

precipitate by 

